JP4741272B2 - Dynamic load measuring device - Google Patents

Description

  The present invention relates to a dynamic load measuring device essential for evaluating characteristics of an impact absorbing member typified by an automobile structure.

  In recent years, in the automobile industry, the development of a vehicle body structure that can reduce injury to passengers during a collision has become an urgent issue. Such a vehicle body structure is composed of a plurality of members, but in order to optimize the collision deformation behavior of the vehicle body, it is extremely important to know the deformation characteristics of the individual members or a combination of some of them. .

  Until now, deformation characteristics of members have often been performed by a quasi-static method. Specifically, the characteristics have been evaluated by deforming the member at a low speed using a large compression tester or the like. However, the actual collision deformation occurs at a high speed and is different from the behavior under a quasi-static load. In particular, it is known that buckling, which is important in a thin plate structure often used in automobiles, behaves differently depending on whether the load is dynamic or quasi-static. In view of this, drop weight tests are often performed to grasp dynamic deformation characteristics. This is to cause dynamic deformation by causing a falling weight to collide with the fixed member from above.

  By using such means, the deformation comes close to that at the time of actual collision, but actually it is necessary to evaluate the absorbed energy at the time of impact deformation of the member. In order to evaluate the absorbed energy, it is necessary to measure the crushing distance of the member and the crushing load at that time. In the case of a dynamic test, measurement of this crushing load is very difficult. In general, when trying to measure a dynamic load with a load cell used in a normal quasi-static test, the shock elastic wave reflects and propagates through the load cell during measurement, so vibration caused by this propagation is superimposed on the measured load. As a result, true load measurement cannot be performed.

  With respect to such a dynamic load measuring method, several proposals have been made as methods for measuring the stress-strain relationship of materials. For example, as described in Non-Patent Document 1, etc., the so-called Kolsky method, which makes it possible to measure only the load at the time of test deformation by allowing a shock elastic wave to escape in the longitudinal direction of the rod with an elongated elastic rod, is a high-speed deformation method. Known as a test method. However, this test method was devised to measure the stress-strain relationship of materials, and the test equipment is huge when trying to cope with the long measurement time and large loads required for dynamic testing of members. In reality, it is impossible to configure the test apparatus, and even if it is realized, it is difficult to maintain and manage accuracy, and deep experience and knowledge are required to obtain highly accurate data.

On the other hand, as shown in Patent Document 1, an impact test composed of an insulating means for blocking the propagation and transmission of stress waves from the base to a small protrusion protruding on the block-like base An apparatus is disclosed. This device measures the load with a small protrusion smaller than the base, but there is no influence of stress waves propagating through the small protrusion, and the insulating means blocks the propagation and transmission of stress waves between the base and the outside. It is shown that measurement can be performed at a high strain rate. However, it is generally difficult to select an insulating means for preventing the propagation of stress waves, and no specific method is disclosed. In addition, there is no technical disclosure regarding a member that generates a larger load than a material test piece such as a member to be used in the present invention.
Japanese Patent Laid-Open No. 10-30980 SAE TECHNICICAL PAPER # 960019 (issued in October 1996, Publisher: Society of Automotive Engineer)

  The present invention relates to an apparatus that simply provides a method for accurately measuring a load of a test specimen in measurement of dynamic deformation characteristics of a shock absorbing member typified by an automobile structure. Here, the test specimen refers to a structure constituted by a single member or a plurality of members.

The present inventors have studied paying attention to the propagation characteristics of stress waves during test execution, placing the load detection unit as close as possible to the load to be measured, and supporting the load detection unit and the load detection unit from the member. It has been found that by appropriately arranging the cross-sectional area of the portion connected to the supporting structure, dynamic load can be measured by a relatively simple means. The gist of the present invention is as follows.
(1) A device for measuring the dynamic deformation characteristics of a test body, in which the action start point of a dynamic load and the support structure of the load detection unit are linearly arranged, and the action start point, the test body, and the load detection The support structure of the load detector adjacent to the load detector and the load detector is arranged in this order, and the load detector is cylindrical, and the ratio of the diameter D (mm) to the length L (mm) Satisfying 0.3 ≦ L / D ≦ 3, 30 mm ≦ L ≦ 300 mm , 80 mm ≦ D , and 5 × (the cross-sectional area of the load detector ) <(the load detector adjacent to the load detector) A dynamic load measuring device characterized by satisfying the cross-sectional area of the support structure.
(2) A device for measuring the dynamic deformation characteristics of a test body, in which an action starting point of a dynamic load and a support structure of a load detection unit are linearly arranged, and the action starting point, the test body, and the test body The support structure of the load detection section adjacent to the load detection section , the load detection section, and the load detection section is arranged in this order, and the load detection section is cylindrical, and its diameter D (mm) and length The ratio of L (mm) satisfies 0.3 ≦ L / D ≦ 3, 30 mm ≦ L ≦ 300 mm , 80 mm ≦ D , and 5 × (the cross-sectional area of the load detection unit ) <(the load detection unit and adjacent, the cross-sectional area of the support portion of the specimen), the dynamic load and satisfies the (cross-sectional area of the load detection portion) <(adjacent to the load detection unit, the cross-sectional area of the support structure of the load detecting unit) Measuring device.
(3) The dynamic load measuring device according to (1) or (2) , wherein the load detecting unit and the support structure of the load detecting unit adjacent to the load detecting unit are integrated.
(4) Furthermore, the support structure of the test body adjacent to the load detection section, the load detection section, and the support structure of the load detection section adjacent to the load detection section are integrated. Dynamic load measuring device.
(5) In a drop weight test in which a falling weight is dropped and collides with a test body, the test body, the load detection section, and the load detection section support structure adjacent to the load detection section are integrated, fixed to a horizontal plane and fixed. The dynamic load measuring device according to (1), (2), (3) or (4), characterized in that
(6) In the test in which the test body is moved in the horizontal direction and collides with the vertical rigid wall, the support structure for the load detection section adjacent to the test body, the load detection section, and the load detection section is integrated. The dynamic load measuring device according to (1), (2), (3) or (4), which is movable in a horizontal direction.

  Based on the present invention, high-precision dynamic load can be measured, and reliable dynamic deformation behavior can be provided at the time of overall vehicle design or component design, trial and error in design can be reduced, and the time taken can be shortened. . In addition, it is easy to verify the results of collision simulations that have been introduced in recent years with highly reliable experimental results obtained by this test apparatus, which can be used to expand the application of simulation technology. In addition, the test accuracy can be greatly increased at a lower cost than the conventional test method.

  First, the present inventors diligently studied the conventional high-speed deformation testing method. As a result, it came to mind that one of the differences between the Kolsky method, which provides highly accurate test results, and the hydraulic servo method, which is simple but inaccurate, is in the position of load measurement. To solve this problem, it is first necessary to measure the load near the specimen. In the method disclosed in Patent Document 1, the load measurement is performed near the test piece. However, in order to avoid the influence of the stress wave propagation inside the small protrusion for load measurement, the size is large. Therefore, it is not suitable for measuring the dynamic load of the target member. In addition, this method requires some insulating means between the block-shaped base and the outside.

  When testing at normal deformation speed, the propagation speed of the stress wave propagating through the test piece and the test machine is sufficiently large compared to the test speed, so no matter which section of the load transmission path connected in series is measured, Its value is constant. However, in the dynamic deformation which is now a problem, it cannot be said that the propagation speed of the stress wave is sufficiently high, and accurate load measurement cannot be performed without considering the propagation of the stress wave. When load measurement is performed with a normal load cell, vibration is observed superimposed on a normal waveform, which is due to the influence of stress waves propagating in the test apparatus.

  When a dynamic test is performed, first, stress waves are reflected and interfered inside the specimen, and the deformation inside the specimen is made uniform. Further, although the stress wave propagates to the load detection unit, it is necessary to saturate the internal reflection / interference that causes stress wave noise at an early stage in order to perform high-speed and high-accuracy load measurement. Therefore, it is necessary to shorten the axial length of the load detection unit. This is to reduce the time required for the stress wave to propagate through the entire load detector.

  As a result of further investigations by the present inventors in consideration of the above contents, the change in cross-sectional area between the shape and dimensions of the load detection unit and the load detection unit and the structure supporting it from the test body is greatly increased in measurement accuracy. It has been found to affect. It was found that the dynamic load can be measured with high accuracy by designing and arranging them appropriately. Each will be described below with reference to FIG.

  First, regarding the arrangement around the specimen, the value does not change in principle even if a load is detected at either end of the specimen that is undergoing dynamic deformation. However, when the load is measured at the point of application of the dynamic load, the load to be measured is measured because contact and detachment are repeated between the structure that loads the dynamic load (falling weight in FIG. 1) and the specimen. It will move a lot. On the other hand, since such contact and separation are not repeated on the opposite side of the point of action of the dynamic load across the specimen, stable load measurement is possible. Therefore, in the present invention, the load detection unit is installed on the opposite side of the dynamic load application point, that is, the dynamic load operation start point, the test body, the load detection unit, and the load detection unit support structure are arranged in this order. It was. Moreover, these structures need to be arranged linearly. This is to prevent a bending moment from being generated during dynamic deformation of the specimen when it is not linearly arranged, so that the axial load that is originally intended to be measured is not an incorrect value or the load detector is not damaged. Is necessary.

  Next, the load detection unit is cylindrical, and the range of the ratio L / D between the length L (mm) of the part having the same cross section and the diameter D (mm) is set to 0.3 or more and 3 or less. The shape of the load detection unit needs to be cylindrical because the load distribution in the cross section needs to be uniform in order to measure the load with a strain gauge attached to the surface. Moreover, when L / D becomes smaller than 0.3, the stress of the load detecting portion becomes non-uniform in the cross section, and the difference between the load calculated from the surface strain measured by the strain gauge and the actual load increases. Further, if it exceeds 3, it becomes difficult to cause stress wave saturation inside the load detection section as described above, so the above range is specified.

  Another important point is the arrangement of the cross-sectional areas of the load detector and its support structure. As a result of the diligent study by the present inventors, when the cross-sectional area advances from a large area to a small area, the influence of the disturbance of stress wave propagation is very large in the large cross-sectional area, but the small to large When proceeding to the area, it was found that the small area is hardly affected by the disturbance. In the load detection unit, it is necessary to avoid the disturbance of the stress wave propagating for accurate measurement, and the cross-sectional area of the load detection unit needs to belong to a small region. On the other hand, it is desirable to increase the cross-sectional area change with the support structure in order to quickly saturate the stress wave in the load detector. Taking these two conditions into consideration, (the cross-sectional area of the load detection unit) <(the cross-sectional area of the support structure of the load detection unit).

  In this invention which concerns on said (2), as shown in FIG. 5, the action | operation start point of a dynamic load and its support structure are arrange | positioned linearly. This is because a bending moment is applied to the load detection unit in the same manner as described above, resulting in an illegal measurement value and preventing the load detection unit from being broken.

  Further, the action start point of the dynamic load, the test body, the support part of the test body, the load detection part, and the support structure of the load detection part are arranged in this order. As a result, load measurement is performed on the opposite side across the action starting point and the test body, avoiding the influence of contact and separation between the test body and the dynamic load loading mechanism (falling weight in FIG. 5) at the action starting point, Stable load measurement can be performed.

  Next, when it is necessary to support and fix the test specimen to be tested, (cross-sectional area of the load detection section) <(cross-sectional area of the support section of the test specimen), (cross-sectional area of the load detection section) < It stipulates that the support part of the test body that satisfies (the cross-sectional area of the support structure of the load detection part) be installed.

  In order to measure the load with high accuracy, it is better to make the length L and the diameter D of the cylindrical load detection unit as small as possible, but in that case, the size of the test body that can be installed in the load detection unit is limited. . When measuring the dynamic load of a relatively large specimen, it is desirable not to increase the size of the load detector, but to provide a support for the specimen, in which case the cross-sectional area of the support is the load detector. It is necessary that (the cross-sectional area of the load detection portion) <(the cross-sectional area of the support portion of the test body) so as not to cause disturbance of the stress wave. In addition, when the specimen is dynamically deformed, the buffer part (cross-sectional area of the load detector) <(support of the specimen) is also used when the contact portion of the specimen with the cylindrical load detector becomes extremely uneven. It is desirable to provide a support portion that satisfies the sectional area of the portion. As a result, a uniform load can be applied to the load detector in the axial direction within the cross section.

  Further, similarly to the invention according to (1), (the cross-sectional area of the load detection unit) <(the cross-sectional area of the support structure of the load detection unit). This is because the change in the cross-sectional area between the support structure and the load wave detector is saturated early and the stress wave progresses from a small area to a large area. Two conditions that the load detection unit belongs to a small area are taken into consideration because it is hardly affected by the disturbance.

  The reason for limiting the ratio L / D between the length L and the diameter D of the load detection unit is the same as that of the invention according to the above (1).

  In this invention which concerns on said (3), the support structure of a load detection part and a load detection part is integrated. This is to prevent unexpected reflection of stress waves between the load detection unit and the load detection unit support structure, and whether the load detection unit and the load detection unit support structure are manufactured integrally, Mechanical fixation or welding is desirable.

  In this invention which concerns on said (4), the support part of a test body, the load detection part, and the support structure of a load detection part are integrated. This is to prevent unexpected stress wave reflections between the load detector, the load detector support structure, and the test specimen support, and the test specimen support, load detector, and load. It is desirable to manufacture the support structure of the detection unit integrally, or to mechanically fix or weld it.

  In the present invention according to the above (5), when performing a dynamic test with the test body stationary as in the drop weight test, from the action starting point at which a dynamic load is applied to the test body, the test body, the load detection unit, It is preferable that the support structure of the load detection unit is arranged in this order, and the test body, the load detection unit, and the support structure are fixed integrally and are immovable. This is because when a dynamic load is measured near the action start point, it is easily affected by the fluctuation of the load load, so this structure allows the load to be measured on the opposite side of the specimen from the action start point. This is because high-precision dynamic load measurement is possible.

  In this invention which concerns on said (6), when performing a dynamic test by making a test body movable like a bogie test, from a starting point which gives a dynamic load to a test body, a test body, a load detection part, a load It is preferable that the support structure of the detection unit is arranged in this order, and the support structure of the test body, the load detection unit, and the load detection unit is integrally fixed and movable. This is the same as (5). When dynamic load is measured in the vicinity of the action start point, it is easily affected by fluctuations in the load, so this structure measures the load on the opposite side of the specimen from the action start point. This is because the dynamic load can be measured with high accuracy.

  The above description has been made on the assumption that each part constituting the test apparatus is of the same material, that is, the elastic modulus and the density are the same, but when the material of each part is different, not only the cross-sectional area but also the acoustic impedance is set. It is necessary to consider together. The acoustic impedance is expressed by the product of the material density and the stress wave (= elastic wave) propagation velocity. Therefore, when different types of materials are used, the present invention can be used by replacing the description of the cross-sectional area with the value of (cross-sectional area) × (density) × (stress wave propagation velocity).

  The length L of the load detection part is 200 mm or less, preferably 100 mm or less. This is because not only the ratio of L and D with respect to the propagation of the stress wave, but also the absolute value of the length of L with respect to the propagation speed of the stress wave becomes a problem. D is determined from the assumed maximum load. Specifically, the material obtained by multiplying the yield stress of the material of the stress detection section by the cross-sectional area is set to be equal to or less than the maximum load. Desirably, this calculated value is 50% or more of the maximum test load.

The technical contents of the present invention will be described below with examples.
The schematic diagram of the apparatus used for FIG. 1 is shown. A dynamic test specimen was subjected to an axial crush test using the falling weight 5. The weight of the falling weight 5 was 800 kg, and the falling height was 2 m. Moreover, what measured the displacement of the falling weight 5 with the laser type displacement meter installed in the lower part as the displacement of the test body 1 was used. Although the conditions for the falling weight 5 were the same, a test using a conventional load cell was also performed as a comparative example. In this example, a 590 MPa class steel plate having a thickness of 2 mm was used as the test body 1 and a 70 mm square tube having a length of 300 mm was used. FIG. 2 shows a schematic diagram of the load measuring apparatus of the present invention. In the load measuring apparatus of the present invention, the load is measured from the elastic strain of the cylindrical load detecting unit 3. As a means for detecting the elastic strain, a strain gauge attached to the central portion in the axial direction of the load detecting unit 3 is used. It was. This is common to all experiments.

  Table 1 shows the measurement conditions and the results. In FIG. The result of having performed the test on condition 3 is shown. At the same time, a test result using a conventional load cell is shown as a comparative example. While the value of the conventional load cell is an inaccurate value including stress wave noise, the load measuring device of the present invention can measure with high accuracy. In this study, in order to grasp the influence of the dimensions of the load detection device, a drop weight test was performed under the same conditions, and tests were performed using various load measurement devices. No. As shown in FIG. 8, when L / D is 4.0 and exceeds the upper limit of the present invention according to (1), saturation of the stress wave in the load detection part within the measurement time is not sufficient, and the result is shown in FIG. Some stress wave noise similar to the conventional load cell measurement waveform was observed. No. When L / D is 0.25 and lower than the lower limit of the present invention according to (1) as in 1, there is no problem of stress wave noise, but when the load to be measured is small, within the cross section of the load detector The elastic deformation was not uniform, and the measured load at a low load was smaller than the actual load. Good measurement was possible under other conditions. No. No. 9 was tested by reducing the cross-sectional area of the support portion of the load detection unit, but vibration was observed in the measurement waveform and load measurement with high accuracy could not be performed.

  The same drop weight testing machine as in Example 1 was used. However, as shown in FIG. 4, a hat-shaped member having a relatively large cross section was used as a test body, and a load measuring device equipped with a support portion for the test body was used. A test was conducted. A schematic diagram of the test apparatus is shown in FIG. The falling weight was 800 kg and the falling height was 2 m. A schematic diagram of the load measuring apparatus of the present invention is shown in FIG. The hat member was manufactured using a 590 MPa class steel plate having a thickness of 2 mm and had a length of 300 mm. The hat part and the back plate were joined by spot welding. At that time, the spot welding interval was 45 mm.

  Table 2 shows the measurement conditions and the results. In FIG. The result of having performed the test on 12 conditions is shown. At the same time, a test result using a conventional load cell is shown as a comparative example. While the value of the conventional load cell is an inaccurate value including stress wave noise, the load measuring device of the present invention can measure with high accuracy even when the support portion of the test body is included. . When the ratio L / D of the dimension of the load detection part is less than 0.3 and when it exceeds 3, the test results are inferior as in Example 1. Except for this, it has been found that the load measuring device of the present invention can provide good test results even when there is a support for the test specimen.

  FIG. 8 shows a schematic diagram of the cart test. The specimen used was the same as in Example 2 (FIG. 4). The test body and the load measuring device are fixed to a 180 kg hammer 9, and the hammer 9 is movable along the rail 10. The load measuring device (the test piece support portion 8, the load detection portion 3, the load detection portion support structure 4) and the test piece 1 are fixed to the hammer 9 as shown in FIG. Injected at s and collided with the rigid wall. At this time, the load measuring device (the test body support section 8, the load detection section 3, and the load detection section support structure 4) having the test body support section 8 was also attached to the rigid wall side. The load detectors on the test body side and the rigid wall side have the same dimensions, and the load detectors L and D are 40 mm and 85 mm, respectively (L / D = 0.47). Further, the support portion 8 of the test body and the support structure 4 of the load detection portion were 200 square and 50 mm thick.

  FIG. 9 shows the test results. Although good test results have been obtained with any of the load measuring devices, the load measuring device installed on the rigid wall side is affected by the fluctuation of the load load and shows some vibration. Thus, in the vicinity of the point of action of the dynamic load on the test body, it is easy to be affected by such swinging, so it is desirable to measure the load on the opposite side across the test body.

A schematic diagram of a drop weight test device is shown. The schematic diagram of the load measuring device of the example of the present invention is shown. The measurement result by the example of this invention and a comparative example is shown. The cross-sectional shape of the member used for experiment is shown. The schematic diagram of the drop weight test apparatus containing the support part of a test body is shown. The schematic diagram of the load measuring device of the example of this invention containing the support part of a test body is shown. The measurement result by the example of this invention is shown. The schematic diagram of a trolley | bogie test apparatus is shown. The measurement result by the example of this invention is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Test body 2 Action start point of dynamic load 3 Load detection part 4 Support structure of load detection part 5 Falling weight 6 Displacement meter 8 Strain gauge attaching position 8 Test specimen support part 9 Hammer 10 Rail

Claims (6)

An apparatus for measuring dynamic deformation characteristics of a test body, wherein an action start point of a dynamic load and a support structure of a load detection unit are linearly arranged, and an action start point, a test body, a load detection unit, and The load detection unit support structure adjacent to the load detection unit is arranged in this order, and the load detection unit is cylindrical, and the ratio of the diameter D (mm) to the length L (mm) is 0. 3 ≦ L / D ≦ 3, 30 mm ≦ L ≦ 300 mm , 80 mm ≦ D , and 5 × (the cross-sectional area of the load detection unit ) <(the load detection unit adjacent to the load detection unit) Dynamic cross-sectional area). A device for measuring the dynamic deformation characteristics of a test body, in which an action starting point of a dynamic load and a support structure of a load detection unit are linearly arranged, and the action starting point, the test body, and a support part of the test body The load detection unit and the load detection unit support structure adjacent to the load detection unit are arranged in this order, and the load detection unit is cylindrical, and its diameter D (mm) and length L (mm) ) Satisfies the following condition: 0.3 ≦ L / D ≦ 3, 30 mm ≦ L ≦ 300 mm , 80 mm ≦ D , and 5 × (the cross-sectional area of the load detection unit ) <( adjacent to the load detection unit, A dynamic load measuring device satisfying the following condition: (cross-sectional area of supporting part of test specimen), (cross-sectional area of load detecting part) <(cross-sectional area of supporting structure of load detecting part adjacent to load detecting part). 3. The dynamic load measuring device according to claim 1, further comprising a load detecting unit and a support structure for the load detecting unit which are adjacent to the load detecting unit. 3. The dynamic detecting device according to claim 2, further comprising: a supporting portion of the test body adjacent to the load detecting portion, a load detecting portion, and a supporting structure of the load detecting portion adjacent to the load detecting portion. Load measuring device. In the drop test where the falling weight is dropped and collides with the test body, the test body, the load detection unit, and the load detection unit support structure adjacent to the load detection unit are integrated, fixed to a horizontal plane and fixed. The dynamic load measuring device according to claim 1, 2, 3, or 4. In a test in which the test body is moved in the horizontal direction and collides with a vertical rigid wall, the test body, the load detection unit, and the load detection unit support structure adjacent to the load detection unit are integrated in the horizontal direction. 5. The dynamic load measuring device according to claim 1, 2, 3 or 4, which is movable.

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